In the so-called "power and free" conveyor systems with a continuously moving chain loop, the individual conveyor units or trolleys, which are moved by the chain, are usually latched to the chain for a driving relationship and must be unlatched to stop the individual units. Some systems are designed such that if a stack-up occurs, that is several units bump into each other when a leading unit is stopped, the contact of one following unit with the unit ahead of it will unlatch the following unit from the moving chain. The free unit must be again latched into the chain in order for forward motion to resume.
It is an object of the present invention to provide a moving chain conveyor system for conveyor units which has the equivalent function of a power and free conveyor but has a chain relationship with the moving units such that no latching or delatching is required to effect movement or non-movement of the suspended units.
Briefly, this is accomplished by providing rail suspension of the conveyor units, whether they be part hangers, buckets, or other carrier devices, and providing on each unit a set of three chain engaging gears or sprockets on parallel axes, one being on an axis offset from the other two so that there is an over-and-under relationship of the chain to the sprockets. This relationship causes the units to move with the chain unless mechanically blocked. If it is blocked, the chain will turn the sprockets and the particular unit will remain stationary. When the unit is released, it will again move with the chain.
In U.S. Pat. No. 4,227,609 (1980), there is shown a bucket conveyor with a looped chain or rope to drive the buckets but these buckets are fixed on the chain with no concept of relative motion with respect to the chain except to allow the bucket to swing relative to the axle on which it is located. In U.S. Pat. No. 3,968,754 (1976), a loop chain construction utilizes the main and upper sprocket as a drive so the mining machine pulls itself along the chain. A similar disclosure is found in U.S. Pat. No. 4,235,475 (1980), and U.S. Pat. No. 3,892,184 (1975).
Another feature of the invention lies in a system which allows tightening of the closed drive chain loop to increase the drive relationship of the chain to the over-and-under loop at each conveyor unit. Chain tightening devices are known in patents of which U.S. Pat. No. 4,284,192 (1981) is representative but the present combination to be disclosed utilizes the chain tightening for a significantly different purpose.
Other objects and features of the invention will be apparent in the following description and claims in which the invention is set forth, together with details to enable persons skilled in the art to practice the invention, all in connection with the best mode presently contemplated.